There are different places in MediaWiki that a semicolon is used to separate list of usernames, separate a timestamp from a page name, etc.
These are done using hard-coded strings of semicolon followed by space, '; ', which cannot be localized, as is required for languages that use the Arabic and Syriac scripts, including Persian. Persian uses a different Unicode character for semicolon, namely U+061B, ARABIC SEMICOLON.
Example of such could be seen here:
(search for ;)
All uses of semicolon that is displayed to the user should be localizable. I guess this could be best achieved by definining a localizable string name "semicolon-separator" defaulting to "; ".
I am working on a patch.